Method for the manufacture of cord



Feb. 4, 1969 R. s. GOY

METHOD FOR THE MANUFACTURE OF CORD Filed April 24, 1967 United StatesPatent 20,307/66 US. Cl. 57157 10 Claims Int. Cl. D02g 3/02; D01h 13/26,7/02 ABSTRACT OF THE DISCLOSURE I A method for manufacturing a doubledcord using a hollow spindle capable of rotating at high speed. A twistedcontinuous filament yarn, carried on the spindle, is passed down thecentre of the spindle together with an untwisted continuous filamentyarn whilst the spindle is rotated at high speed. The rotation of thespindle causes twist to be removed from the twisted yarn and the twoyarns to become doubled together in a cord.

The rate of input of untwisted yarn must be greater than the rate oftake-up of cord to allow for the apparent reduction in length of theyarnduring doubling.

This invention relates to a method for the. manufacture of cord andparticularly to a method for the manufacture of cord by doublingtogether continuous-filament yarns. By the term continuous-filament yarnas used throughout this specification there is meant a monoormultifilament yarn, or a tape made by splitting uniaxially drawn film.

According to the present invention a method for the manufacture of acord comprises passing together longitudinally through a rotating hollowspindle a continuousfilament yarn initially substantially free fromtwist and a continuous-filament yarn initially in a twisted condition,and drawing off the resulting cord at a rate which is less than the rateat which the yarn initially substantially free from twist is supplied tothe hollow spindle, the yarn initially in a twisted condition beingcarried by the hollow spindle and the hollow spindle being rotated tocause the initially twisted yarn to unwind therefrom and to becomedoubled with the yarn initially substantially free from twist.

According to the present invention also there is pro vided a cordcomprising continuous filaments when manufactured by the methodaccording to the immediatelypreceding paragraph.

Methods used heretofore for manufacturing doubled cord have involvedimposing twist in two single yarns to be doubled together, andsubsequently doubling the two yarns together in such a manner that theinitial twist in the single yarns is removed whilst at the same time thetwo yarns are each given a doubling twist i.e. each is caused to adopt aspiral configuration. This process is laborious and expensive in that itinvolves preparing two packages of twisted yarns, assembling the twopackages side by side on a doubling frame, doubling the two yarnstogether and collecting the doubled yarn on a further package. Doublingis usually effected by down-twisting which involves the use of aring-traveller, or by up-twisting which involves the use of a flyer.Disadvantages of both these methods are that the speed of the process iscontrolled by the maximum speed at which the ringtraveller or flyer canoperate, and also it is difficult to control the uniformity of theresulting cord.

The present invention provides a process in which it is necessary onlyto twist one of the single yarns, i.e. only half of the number ofpackages of twisted yarns need be produced. The process has a furtheradvantage that the speed thereof is not limited to the speed of aringtraveller or a flyer. In order to obtain satisfactory doubling bythe method of the present invention it is necessary merely to obtain thecorrect ratio of spindle speed to yarn throughput; spindle speeds atleast twice as great as those of conventional doubling apparata can beused.

The yarn initially in a twisted condition is carried by the hollowspindle and will usually be in the form of a yarn package such as acop-wound bobbin. The hollow spindle and bobbin may be integral orseparate and in the latter case the bobbin is mounted on and driven bythe spindle. The rotation of the hollow spindle is such that I the factthat the yarn unwinding from the spindle is attached to'the other yarn,it is caused to balloon ofi the spindle as it un-winds.

The yarn which initially is in an untwisted condition is passed directfrom feed rollers through the hollow spindlev substantially parallel tothe longitudinal axis Due to the tension in the balloon of the yarninitially in a twisted condition a twisting action is produced on theyarn initially in the untwisted condition, and this yarn becomes twistedbetween the feed rollers and the spindle but as it is doubled togetherwith the twisted yarn unwinding from the spindle, the twist imposed inthe initially untwisted yarn is removed as is the twist in the twistedyarn, and the initially untwisted yarn and the twisted yarn unwindingfrom the spindle adopt an identical helical path.

The yarn initially in an untwisted condition is fed into the spindle ata constant rate, and the resulting cord is drawn 0d at the bottom of thespindle also at a constant rate. The rate of feed-in of the yarn isgreater than the rate of take-up of the cord, but the two will be in aconstant ratio for a given speed of feed-in. The difference in the ratesis to allow the apparent shortening of the yarn due to its being causedto adopt a helical path in the doubled cord.

The control which the present invention enables to be exercised overboth the feed-in and take-up rates is advantageous in that it enables adegree of control to be exercised over the uniformity of the doubledcord. A disadvantage of the prior processes discussed above is thateither the rate of feed-in of yarn is controlled and not the rate oftake-up (down-twisting) or vice-versa, (up-twisting), and this tends toresult in irregularities in the resulting cord. Although there is nodirect control in the method of the present invention over the rate offeed- I in of the twisted yarn unwinding from the spindle it has beenfound that providing the speed of rotation of the spindle issufficiently high, irregularities due to non-uniform feed-in of thisyarn do not tend to arise. Spindle speeds in excess of 5000 r.p.rn. arepreferred and speeds of up to about 9000 rpm. can be attained.

As hereinbefore stated the yarn initially in a twisted condition becomessubstantially free from twist (other than doubling twist) during thedoubling operation. The yarn initially in an untwisted condition becomestwisted prior to entry into the spindle. This twist imposed on theinitially untwisted yarn is removed during doubling so that in the cordboth yarns are substantially untwisted but each has the same helicalarrangement.

The important features to obtain a uniform yarn are the spindle speedand the rate of throughput of the yarns. It is usual to fix the spindlespeed and to adjust the rate of throughput of the yarns accordingly. Theactual dou bling step is the same as in conventional methods, i.e., itinvolves the doubling together of two twisted yarns in such a way thatthe twist in the individual yarns is re moved. However, the method ofthe present invention has the advantage that due to the control it ispossible to exercise over rate of feed-in and take-up, a cord of greatertwist uniformity can be produced.

As hereinbefore stated the rate of production of a doubled cord byconventional techniques is controlled by the speed of a ring-travelleror a fiyer. The speed is limited due to the fact that the ring-travelleror the flyer moves in contact with a metal surface and the frictionalforces developed result in build-up of heat which if it becomesexcessive could result in stoppage of the machine. Spindle speeds of upto about 4000 rpm. are the maximum which could be expected fromconventional apparatus. As hereinafter explained, the present inventionis not limited in this way and high spindle speeds, and correspondinglyhigh rates of production of cord are possible. For example, using aspindle speed of 6700 r.p.m. carrying a yarn of twist 12.4 turns perinch, it is possible to draw cord off from the bottom of the spindle ata rate of yards per minute.

The present invention is applicable to the production of cords from anysynthetic continuous filaments, e.g., rayon, but it is particularlyapplicable to the production of cord from thermoplastic filaments sinceit is possible in this case to heat-set the resulting cord. Usually,both the initially twisted yarn and the initially untwisted yarn aremultifilament yarns but it is to be understood that, if desired, bothyarns can be a single monofilament yarn, or one yarn can be monofilamentand the other multifilament. In the case where a multifilament yarn isused it is not necessary to employ yarns in which all the filaments arethermoplastic to make a cord which can be heat-set and, in fact, aslittle as 10 percent of the filaments need be thermoplastic in order toconfer heat-settability on the yarn. Examples of suitable thermoplasticfilaments are nylon, poly(ethylene terephthalate) and polypropylene.

The present invention has the further advantage that due to the controlwhich can be exercised over cord drawoff it enables the cord prior towind-up to be treated by any conventional textile processing technique.For example, the cord can be dyed, coated or rubberized prior towind-up. A particularly suitable technique is to pass the cord directlyinto a fluidized bed of solid particles which can conveniently be heatedat an elevated temperature, for example, 250 C., to heat-set the cord.Stretching of the cord during passage through the fluidized bed of solidparticles followed by heat-setting can advantageously be performed toproduce a heat-set cord which is less susceptable to shrinkage orexcessive stretching than a cord which has not been subjected to thetreatment. By heatsetting or hot-stretching the cord immediately afterdoubling, before the foldings have adopted a permanent set, any smallnon-uniformity, produced for instance by slight maladjustment of themachine, will be reduced.

The method of the present invention is particularly applicable to theproduction of tyre cor-ds, especially when the process involvestreatment with a fluidized bed of solid particles as described above. Itis a particularly desirable feature of tyre cords that there should belittle tendency for the cord to untwist (i.e., it should be heatset) andexcessive potential stretching or shrinking of the cord should beavoided. The present invention enables the production of a cor-d whichfulfils each of these requirements.

One form of apparatus suitable for performing the process of the presentinvention will now be described by way of example only, with referenceto the accompanying drawing in which FIGURE 1 is a diagrammaticrepresentation of an apparatus for supplying a twisted yarn on to ahollow spindle and subsequently doubling the twisted yarn with anuntwisted yarn.

As shown in FIGURE 1, a combined bobbin and hollow spindle 1 isvertically mounted in a bearing 2 and is encircled by a ring 3 on whichis slidably carried a traveller 4. Above the centre of the hollowspindle is mounted a pigtail guide ring 5 and a guide roller 12 which isadjacent a system of feed rollers 6. Below the centre of the hollowspindle 1 is mounted a take-off nip roller system 7.

In operation, to form a cop-build of twisted yarn 8 on the combinedbobbin and spindle 1, a yarn 9 is drawn through the feed roller system 6over the guide roller 12, through the pigtail guide ring 5, along thepath 10 (shown as a dotted line), through the traveller 4 and on to thecombined bobbin and spindle 1 by rotation of the spindle 1. The movementof the yarn 9 through the traveller 4 causes the traveller 4 tocircumnavigate the spindle by sliding on the ring 3 and thereby insertstwist into the yarn.

In operation, to double the twisted yarn with a further yarn, a yarn 9,together with the twisted yarn 11 from the combined bobbin and spindle1, is fed through the centre of the hollow spindle 1. The combinedbobbin and spindle 1 is rotated to remove the twist from the twistedyarn 11 and to double wrap this yarn with the yarn 9. The twisted yarn11 thus becomes untwisted and doubled together with the yarn 9 and theresulting cord 12 is taken off by the nip-roller system 7.

During this operation, it is to be noted that the rate at which the yarn9 is fed from the feed roller system 6 is greater than the rate at whichthe cord 12 is taken up by the nip-roller system 7 owing to the apparentdecrease in length resulting from the helical path taken by the yarn 9when doubled with the yarn 11 in the cord 12.

The relation between the speed of rotation of the combined bobbin andthe hollow spindle 1 and the rate of feed of the yarn 9 determines theamount of twist removed from the yarn 11. The number of turns per inchin the doubled cord obtained is also determined by the relationshipbetween the rate of feed of the yarn 9 and the speed of .rotation of thecombined bobbin and spindle 1. Thus, for example, if the speed ofrotation of the spindle is kept constant, the number of doubling turnsper inch in the cord may be increased by lowering the rate of feed ofthe yarn 9. But it is to be noted that in this case more twist would betaken out of the yarn 11 and therefore to maintain twistless yarn in thedoubled cord, the amount of twist initially in the yarn 11 would need tobe greater.

For a tyre cord, the optimum condition is that wherein the yarns in thecord contain no residual twist and in the method of the presentinvention this may be achieved by previously putting into the yarn 11forming the cop build of twisted yarn 8 exactly that amount of twistwhich will be removed by the rotation of the spindle 1. However ifdesired the method of the present invention may be used to produce cordwherein pre-determined amounts of residual twist are retained by theconstituent yarns.

The invention is illustrated by the following example.

EXAMPLE An 840 denier multi-filament nylon 66 yarn consisting ofmono-filaments each of denier 6 was twisted with 12 turns per inch bydown-twisting using a ringtraveller, and was collected on a bobbin. Thebobbin was mounted on a hollow spindle of diameter ins. in such a waythat the bobbin was carried by the spindle and rotated with the spindle.

A multi-filament nylon 66 yarn consisting of 840 monofilaments each ofdenier 140 completely free from twist was wound from a package throughnip rollers and through the hollow spindle parallel to the longitudinalaxis of the spinde, and through take-up rollers.

The free end of the twisted yarn from the bobbin was attached at theentrance to the spindle to the untwisted yarn. The spindle was caused torotate at a speed of 6,700 rpm. and at the same time the untwisted yarnwas passed through the spindle. The rate of feed-in of the yarn was 17.7yards per minute and the rate of drawoff of the resulting cord was 15.3yards per minute. The cord was wound up on a bobbin and a length thereofwas examined.

The properties of the cord are shown in Table I below. In Table I theresult given for doubling twist indicates the number of turns per inchof each yarn in the cord and is irrespective of the singles twist (ifany) in the individual yarns. The results for singles twist weredetermined as follows. A length of the cord was cut off and one of theyarns was removed leaving a single yarn which retained its helicalconfiguration. This helical configuration was removed by twisting in theopposite sense and this twisting induced a singles twist in the yarn. Itis this singles twist which is quoted in Table I, but it is to beunderstood that in the cord each yarn was substantially free fromsingles twist. The results given as percentage coefficient of variationof folding twist represent the percentage maximum variation from themean obtained over a number of determinations.

A sample of the cord prepared as above was then passed through afluidized bed of glass particles which were maintained at a temperatureof 240 C. The rate of feed-in of the cord was yards per minute and thestretch applied to the cord was 8 percent. The cord was heat-set whilststretched by this treatment. The properties of this card are also shownin Table I below.

Having now described my invention, what I claim is:

1. A method for the manufacture of a cord which comprises passingtogether longitudinally through a rotating hollow spindle a positivelyfed continuous-filament yarn initially substantially free from twist anda continuousfilament yarn initially in a twisted condition, and drawingoff the resulting cord at a rate which is less than the rate at whichthe yarn initially substantially free from twist is supplied to thehollow spindle, the yarn initially in a twisted condition being carriedby the hollow spindle and the hollow spindle being rotated to cause theinitially twisted yarn to unwind therefrom and to become doubled withthe yarn initially substantially free from twist.

2. A method according to claim 1 in which the speed of rotation of thehollow spindle is greater than 5,000 r.p.m.

3. A method according to claim 2 in which the speed of rotation of thehollow spindle is up to 9,000 r.p.m.

4. A method according to claim 1 in which both the yarn initiallysubstantially free from twist and the yarn initially in a twistedcondition are multifilament yarns.

5. A method according to claim 1 in which both the yarn initiallysubstantially free from twist and the yarn initially in a twistedcondition are monofilament yarns.

'6. A method according to claim 1 in which at least one of the yarnscomprises a non-thermoplastic filament.

7. A method according to claim 1 in which at least one of the yarnscomprises a thermoplastic filament.

8. A method according to claim 1 which includes the step of heat-settingthe yarns after they have become doubled together.

9. A method according to claim 8 in which the steps of heat-setting theyarns is carried out by passing the cord through a fluid-bed heated toan elevated temperature.

10. A method according to claim 1 in which the yarn initiallysubstantially free from twist is supplied to the hollow spindle at aconstant rate bearing a constant ratio to the rate at which the cord isdrawn off.

References Cited UNITED STATES PATENTS 2,338,656 1/1944 McNally et al.57-18 2,729,050 1/1956 Honig 57--59 XR 3,052,989 9/1962 Doleman 34-573,328,946 7/1967 Schumann et a1. 57-18 FOREIGN PATENTS 200,773 6/ 1955Australia. 1,270,065 7/ 1961 France.

269,421 4/1927 Great Britain.

907,441 10/ 1962 Great Britain.

942,211 11/1963 Great Britain.

STANLEY N. GILREATH, Primary Examiner.

W. H. SCHROEDER, Assistant Examiner.

US. Cl. X.R.

